A variety of studies of proteins within the CNS utilizing 2-dimensional gel electrophoresis (2DE) continue. First, we have shown that intraventricular injection of the brain with 5HT neurotoxin 5,7-dihydroxytryptamine resulted in a decrease in the concentration of 3 different proteins in the parietal cortex and hippocampus. Two hippocampal proteins were elevated in concentration following 5HT depletion. Second, administration of estradiol to 25 day old female rats resulted in changes in protein concentration of the arcuate nucleus-median eminence complex. We have also identified 21 proteins within this area that are altered in relative turnover rate following estradiol treatment. Third, a variety of human brain tumors were found to have characteristic protein profiles that set it apart from the other tumors studied. Fourth, using immunoblotting and comigration techniques, this study describes the identification of twelve major protein spots seen on 2DE gels of normal cerebral cortex and of certain human brain tumors. Fifth, we have demonstrated that the Beta-subunit of the g protein from both bovine rod outer segment membranes (transducin) and from bovine brain exists as multiple charge isomers. Sixth, iron deficiency in rats resulted in an increase in the concentration of 3 proteins in the caudate nucleus and one decreased. Neuron specific enolase was elevated in the nucleus accumbens and glial fibrillary acidic protein reduced.